It is desirable that designers design articles in a manner that provides for foolproof assembly of articles of manufacture. A term borrowed from the Japanese to describe this method of design is “Poke-Yoke”.
Many fluid manifolds, such as those used for hydraulic brake systems, utilize different diameter threaded ports for ports that are in close geometric proximity to each other. This allows for differentiation between different tubes that are to be connected to different circuits, thereby making assembly more foolproof (because it is impossible to connect a tube to the wrong port). Particularly, the foolproof design prohibits an associated tube nut from threading into the wrong bore. However, the use of different size bores requires more costly machining and requires the bores to be spaced farther apart to fit the spacing requirements of the larger of the tube fittings than would be required if all were uniform and of the smallest possible diameter.